A shot rang out outside the apartment doors. When the police broke down the door, they found a pistol on the kitchen floor, missing one cartridge, one spent cartridge case, and two men with bullet wounds to the head... Who were these seriously wounded people and what happened between them? The circumstances of the case are very mysterious, and operatives of the top-secret commission Sergei Petrenko and Varvara Kononova joined the investigation. They found out that the secret goes back to the distant past, when two students, Valerka and Volodya, were in love with the same girl, the charming Lilya...